1. Technical Field
The present invention relates to a two-speed fluid motor having expandable and contractible fluid pockets formed by a gerotor gearset which includes relatively rotatable and orbital inner and outer gear members having teeth which define the fluid pockets.
2. Background Art
A two-speed fluid motor having expandable and contractible fluid pockets formed by a gerotor gearset is disclosed in U.S. Pat. No. 3,778,198. The gerotor gearset includes a stator member having internal teeth and a rotor member having external teeth. The number of teeth on the rotor member is one less than the number of teeth on the stator member. The rotor member is eccentrically disposed within the stator member and is rotatable and orbital relative to the stator member. The rotor member is supported and guided in its rotating and orbiting movement by the teeth of the stator member. The teeth of the rotor member and the teeth of the stator member define the expandable and contractible fluid pockets.
The motor has a fluid inlet port and a fluid outlet port. A commutator valve directs fluid from the inlet port to certain of the fluid pockets and from other of the fluid pockets to the outlet port. The fluid pressure in the fluid pockets causes the rotor member to rotate and orbit relative to the stator member. The output shaft of the motor is driven by the rotor member.
A spool valve is located upstream of the commutator valve and is movable between two positions. In one position, the spool valve directs inlet fluid flow to the commutator valve, and the commutator valve directs the inlet fluid flow to a certain number of the fluid pockets. In the other position of the spool valve, inlet fluid flow is directed to a lesser number of fluid pockets. When inlet fluid flow is directed to the certain number of fluid pockets, the motor operates in a low speed, high torque mode. In the other position of the spool valve, the motor operates in a high speed, low torque mode.
Another two-speed hydraulic motor with expandable and contractible fluid pockets formed by a gerotor gearset is disclosed in U.S. Pat. No. 4,480,971. As disclosed in U.S. Pat. No. 4,480,971, a commutator valve directs fluid flow to and from the fluid pockets. A switching valve located upstream of the commutator valve is movable between two positions. In one position of the switching valve, four fluid pockets communicate with an inlet port and the motor operates in a low speed, high torque mode. In the other position of the switching valve, only two fluid pockets communicate with the inlet port and the motor operates in a high speed, low torque mode.